forked from extern/nushell
94 lines
2.3 KiB
Rust
94 lines
2.3 KiB
Rust
use crate::commands::WholeStreamCommand;
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use crate::context::CommandRegistry;
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use crate::prelude::*;
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use nu_errors::ShellError;
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use nu_protocol::{Signature, SyntaxShape, UntaggedValue, Value};
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use nu_source::Tagged;
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pub struct Last;
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#[derive(Deserialize)]
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pub struct LastArgs {
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rows: Option<Tagged<u64>>,
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}
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#[async_trait]
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impl WholeStreamCommand for Last {
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fn name(&self) -> &str {
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"last"
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}
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fn signature(&self) -> Signature {
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Signature::build("last").optional(
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"rows",
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SyntaxShape::Number,
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"starting from the back, the number of rows to return",
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)
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}
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fn usage(&self) -> &str {
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"Show only the last number of rows."
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}
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async fn run(
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&self,
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args: CommandArgs,
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registry: &CommandRegistry,
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) -> Result<OutputStream, ShellError> {
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last(args, registry).await
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}
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fn examples(&self) -> Vec<Example> {
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vec![
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Example {
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description: "Get the last row",
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example: "echo [1 2 3] | last",
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result: Some(vec![Value::from(UntaggedValue::from(BigInt::from(3)))]),
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},
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Example {
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description: "Get the last three rows",
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example: "echo [1 2 3 4 5] | last 3",
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result: Some(vec![
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UntaggedValue::int(3).into(),
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UntaggedValue::int(4).into(),
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UntaggedValue::int(5).into(),
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]),
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},
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]
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}
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}
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async fn last(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
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let registry = registry.clone();
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let (LastArgs { rows }, input) = args.process(®istry).await?;
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let v: Vec<_> = input.into_vec().await;
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let end_rows_desired = if let Some(quantity) = rows {
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*quantity as usize
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} else {
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1
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};
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let beginning_rows_to_skip = if end_rows_desired < v.len() {
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v.len() - end_rows_desired
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} else {
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0
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};
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let iter = v.into_iter().skip(beginning_rows_to_skip);
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Ok(futures::stream::iter(iter).to_output_stream())
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}
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#[cfg(test)]
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mod tests {
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use super::Last;
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#[test]
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fn examples_work_as_expected() {
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use crate::examples::test as test_examples;
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test_examples(Last {})
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}
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}
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